[Greenbuilding] Solar Gain from South facing windows

[Corwyn]

On Jun 13, 2007, at 09:45, Tom Wiprud wrote:

> Some other posts have mentioned that low E glass does not reflect the 
> summer
> sun.  Is this true?   I just read in a Marvin window catalog, that Low 
> E
> lets the sun in in the winter, but reflects it out in the summer.    I 
> am
> looking at using Marvin fiberglass Integrity windows, casement and 
> awning
> types on my new house.  Thanks   Tom

While it is possible Marvin has some great new solution to window 
transmittance, it seems more likely they are engaging in marketing.  
Lo-e stands for Low Emissivity.  That is, the measurement of much heat 
is radiated from a surface as a function of its temperature.  How this 
helps is a warm piece of glass will radiate more from a non-coated 
surface than a coated one.  Putting a coating on the outside surface of 
a glass pane (in a multi-pane window) will cause more of the heat lost 
from the glass to go back into the room, rather than outside.

The coating will also have other optical qualities, such as reducing  
UV, IR and visible light transmittance which will be reflected (NPI) in 
the characteristics claimed for the windows (SHGC, Visible 
transmittance, etc.).

You should be able to compare windows (assuming they are all well made) 
from the required performance data.  No real need to look at marketing 
hype.  For instance, how does the window know it is summer?  Does 
Marvin use a different lo-e than everybody else? (Note there are at 
least two types, be sure to get the right type for your climate).

Thank You Kindly,

Corwyn